Display device

ABSTRACT

At least one or more of a conductive layer which forms a wiring or an electrode and a pattern necessary for manufacturing a display panel such as a mask for forming a predetermined pattern is formed by a method capable of selectively forming a pattern to manufacture a liquid crystal display device. A droplet discharge method capable of forming a predetermined pattern by selectively discharging a droplet of a composition in accordance with a particular object is used as a method capable of selectively forming a pattern in forming a conductive layer, an insulating layer, or the like.

TECHNICAL FIELD

The present invention relates to a display device to which an activeelement such as a transistor formed over a glass substrate is appliedand to a method for manufacturing the same.

BACKGROUND ART

Conventionally, a display panel of a so-called active matrix drivingmethod constituted by a thin film transistor (hereinafter also referredto as a “TFT”) over a glass substrate is known. As well as amanufacturing technique of a semiconductor integrated circuit, thisdisplay panel needs a step of patterning a thin film such as aconductor, a semiconductor, or an insulator by a light-exposure stepusing a photomask.

A size of a mother glass substrate used for manufacturing a displaypanel is enlarged from 300 mm×400 mm of the first generation in theearly 1990s to 680 mm×880 mm or 730 mm×920 mm of the fourth generationin 2000. Furthermore, the manufacturing technique made such adevelopment that a number of display panels can be obtained from onesubstrate.

When a size of a glass substrate or a display panel is small, patterningcan be carried out comparatively easily by using a photolithographymachine. However, as a substrate size is enlarged, an entire surface ofa display panel cannot be simultaneously treated by carrying outlight-exposure treatment once. Consequently, it is necessary to divide aregion where a photoresist is applied into a plurality of block regionsand to carry out light-exposure treatment on every predetermined blockregions. As for light-exposure treatment, a method for exposing anentire surface of a substrate to light by sequentially repeating thetreatment has been developed (for example, see Reference 1: JapanesePatent Application Laid-Open No. Hei 11-326951 and 2: U.S. Pat. No.6,291,136 B1).

DISCLOSURE OF INVENTION Problem to be Solved by the Invention

However, a glass substrate is further enlarged to a size of 1000 mm×1200mm or 1100 mm×1300 mm in the fifth generation, and a size of 1500mm×1800 mm or more is assumed in the next generation. A large sizedglass substrate is effective in enlarging a size of display panel andincreasing the number of a display panel to be obtained; however, it isdifficult to manufacture a display panel at good productivity with lowcost by a conventional patterning method. In other words, when aplurality of times of light-exposure is carried out by consecutive lightexposure, a processing time is increased and tremendous investment isrequired for developing a photolithography machine that can treat alarge-sized glass substrate.

Moreover, in a method for forming various types of thin films over anentire surface of a substrate and for removing the thin films to leave aslight region by etching, there is a problem that a material cost iswasted and disposal of a large quantity of effluent is forced.

In view of the above situation, the object of the present invention isto provide a liquid crystal display device capable of improvingutilizing efficiency of a material and of simplifying a manufacturingstep and a manufacturing technique thereof.

Means to Solve the Problem

According to one aspect of the present invention, at least one or moreof a conductive layer which forms a wiring or an electrode and a patternsuch as a mask for forming a predetermined pattern which is necessaryfor manufacturing a display panel is formed by a method capable ofselectively forming a pattern to manufacture a liquid crystal displaydevice. A droplet discharge method (also referred to as a ink-jet methoddepending on a system to be applied) capable of forming a predeterminedpattern by selectively discharging a droplet of a composition inaccordance with a particular object is used as a method capable ofselectively forming a pattern.

According to another aspect of the invention, a method for manufacturinga liquid crystal display device comprises the steps of: forming a gateelectrode over a substrate having an insulating surface with a dropletdischarge method; laminating a gate insulating layer, a semiconductorlayer, and an insulating layer over the gate electrode; forming a firstmask in a position overlapping with the gate electrode with a dropletdischarge method; forming a channel protective layer by etching theinsulating layer by using the first mask; forming a semiconductor layercontaining one conductivity type impurity; forming a second mask in aregion including the gate electrode with a droplet discharge method;etching the semiconductor layer containing one conductivity typeimpurity and the semiconductor layer; forming source and drain wiringswith a droplet discharge method; and etching the semiconductor layercontaining one conductivity type impurity on the channel protectivelayer by using the source and drain wirings as masks.

According to another aspect of the invention, a method for manufacturinga liquid crystal display device comprises the steps of: forming a gateelectrode and a connection wiring, over a substrate having an insulatingsurface with a droplet discharge method; laminating a gate insulatinglayer, a semiconductor layer, and an insulating layer over the gateelectrode; forming a first mask in a position overlapping with the gateelectrode with a droplet discharge method; forming a channel protectivelayer by etching the insulating layer by using the first mask; forming asemiconductor layer containing one conductivity type impurity; forming asecond mask in a region including the gate electrode with a dropletdischarge method; etching the semiconductor layer containing oneconductivity type impurity and the semiconductor layer; partiallyexposing the connection wiring by selectively etching the gateinsulating layer, forming source and drain wirings and connecting atleast one of the wirings to the connection wiring; and etching thesemiconductor layer containing one conductivity type impurity on thechannel protective layer by using the source and drain wirings as masks.

In the above-mentioned step of laminating a gate insulating layer, asemiconductor layer, and an insulating layer over the gate electrode, itis preferable to successively form each layer of the gate insulatinglayer, the semiconductor layer, and the insulating layer withoutexposing to the atmosphere by a vapor phase growth method using plasma(refer to as plasma CVD) or a sputtering method.

By sequentially laminating a first silicon nitride film, a silicon oxidefilm, and a second silicon nitride film to form a gate insulating layer,the gate electrode can be prevented from being oxidized and asatisfactory interface between the semiconductor layer formed over theupper layer side of the gate insulating layer can be formed.

As mentioned above, according to the other aspect of the invention, thegate electrode, the wiring, and the mask used during patterning areformed by a droplet discharge method. However, at least one or morepatterns necessary for manufacturing a liquid crystal display device areformed by a method capable of selectively forming a pattern tomanufacture a liquid crystal display device, thereby achieving theobject. In the invention, a screen printing method capable ofselectively forming a pattern or other printing methods can be alsoapplied instead of a droplet discharge method.

According to the other aspect of the invention, a liquid crystal displaydevice, over one of substrates sandwiching a liquid crystal, comprises:a thin film transistor including a lamination of a gate electrode formedby making fusion and/or welding of (by fusing) conductive nanoparticles,a silicon nitride layer or a silicon nitride oxide layer formed to be incontact with the gate electrode, a gate insulating layer at leastcontaining a silicon oxide layer, and a semiconductor layer from asubstrate side; and a pixel electrode connecting to the thin filmtransistor.

According to the other aspect of the invention, a liquid crystal displaydevice, over one of substrates sandwiching a liquid crystal, comprises:a thin film transistor including a lamination of a gate electrode formedby making fusion and/or welding of (by fusing) conductive nanoparticles,a silicon nitride layer or a silicon nitride oxide layer formed to be incontact with the gate electrode, a gate insulating layer at leastcontaining a silicon oxide layer, a semiconductor layer, and a siliconnitride layer or a silicon nitride oxide layer formed to be in contactwith a wiring connected to a source and a drain and formed by makingfusion and/or welding of (by fusing) conductive nanoparticles from asubstrate side; and a pixel electrode connecting to the thin filmtransistor.

According to the other aspect of the invention, a liquid crystal displaydevice, over one of substrates sandwiching a liquid crystal, comprises:a first thin film transistor having, from a substrate side, a laminationof a gate electrode formed by making fusion and/or welding of (byfusing) conductive nanoparticles, a silicon nitride layer or a siliconnitride oxide layer formed by being contact with the gate electrode, agate insulating layer at least containing a silicon oxide layer, and asemiconductor layer; a pixel electrode connecting to the first thin filmtransistor; a driver circuit including a second thin film transistorformed by having the same layer structure as the first thin filmtransistor; and a wiring extending from the driver circuit andconnecting to the gate electrode of the first thin film transistor.

According to the other aspect of the invention, a liquid crystal displaydevice, over one of substrates sandwiching a liquid crystal, comprises:a driver circuit including a first thin film transistor having alamination of a gate electrode formed by making fusion and/or welding of(by fusing) conductive nanoparticles, a silicon nitride layer or asilicon nitride oxide layer formed to be in contact with the gateelectrode, a gate insulating layer at least containing a silicon nitridelayer or silicon oxynitride layer and a silicon oxide layer, asemiconductor layer, and a silicon nitride layer or a silicon nitrideoxide layer formed to be in contact with wirings connected to a sourceand a drain and formed by making fusion and/or welding of (by fusing)conductive nanoparticles from a substrate side; a pixel electrodeconnecting to the first thin film transistor; a driver circuit includinga second thin film transistor formed by having the same layer structureas the first thin film transistor; and a wiring extending from thedriver circuit and connecting to the gate electrode of the first thinfilm transistor.

According to the invention, the gate electrode or the wiring is formedwith a droplet discharge method, and a conductive substance can beformed from silver or an alloy containing silver. In addition, a siliconnitride film or a silicon nitride oxide film is provided over an upperlayer of the gate electrode or the wiring to be in contact; therefore,the gate electrode can be prevented from being deteriorated due tooxidization.

In the invention, it is also possible that the semiconductor layer,which is a main portion of a thin film transistor, contains hydrogen andhalogen, and is formed from a semi-amorphous semiconductor containing acrystal structure. Accordingly, a driver circuit only including ann-channel type thin film transistor can be provided. In other words, thesemiconductor layer contains hydrogen and halogen and is a semiconductorhaving a crystal structure, thereby realizing the driver circuit overone substrate by the thin film transistor which is capable of beingoperated with electric field effect mobility of from 1 cm²/V·sec to 15cm²/V·sec cm².

Advantageous Effect

According to the present invention, patterning of a wiring or a mask canbe carried out directly by a droplet discharge method; therefore, a thinfilm transistor in which utilization efficiency of a material isimproved and a manufacturing step is simplified, and a liquid crystaldisplay device using the thin film transistor can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a top view illustrating a structure of a liquid crystaldisplay panel according to the invention;

FIG. 2 shows a top view illustrating a structure of a liquid crystaldisplay panel according to the invention;

FIG. 3 shows a top view illustrating a structure of a liquid crystaldisplay panel according to the invention;

FIGS. 4A to 4C each show cross-sectional views illustrating a method formanufacturing a liquid crystal display panel according to the invention;

FIGS. 5A to 5C each show cross-sectional views illustrating a method formanufacturing a liquid crystal display panel according to the invention;

FIGS. 6A to 6C each show cross-sectional views illustrating a method formanufacturing a liquid crystal display panel according to the invention;

FIG. 7 shows a cross-sectional view illustrating a method formanufacturing a liquid crystal display panel according to the invention;

FIGS. 8A and 8B each show cross-sectional views illustrating a methodfor manufacturing a liquid crystal display panel according to theinvention;

FIG. 9 shows a cross-sectional view illustrating a method formanufacturing a liquid crystal display panel according to the invention;

FIGS. 10A to 10C each show cross-sectional views illustrating a methodfor manufacturing a liquid crystal display panel according to theinvention;

FIG. 11 shows a cross-sectional view illustrating a method formanufacturing a liquid crystal display panel according to the invention;

FIG. 12 shows a cross-sectional view illustrating a method formanufacturing a liquid crystal display panel according to the invention;

FIG. 13 shows a top view illustrating a method for manufacturing aliquid crystal display panel according to the invention;

FIG. 14 shows a top view illustrating a method for manufacturing aliquid crystal display panel according to the invention;

FIG. 15 shows a top view illustrating a method for manufacturing aliquid crystal display panel according to the invention;

FIG. 16 shows a top view illustrating a method for manufacturing aliquid crystal display panel according to the invention;

FIGS. 17A and 17B each show a mounting method (a COG method) of a drivercircuit of a liquid crystal display panel according to the invention;

FIGS. 18A and 18B each show a mounting method (a TAB method) of a drivercircuit of a liquid crystal display panel according to the invention;

FIG. 19 shows a cross-sectional view illustrating a liquid crystaldisplay panel according to the invention;

FIG. 20 shows a diagram illustrating a circuit structure in the case offorming a scanning line driver circuit with a TFT in a liquid crystaldisplay panel according to the invention;

FIG. 21 shows a diagram illustrating a circuit structure in the case offorming a scanning line driver circuit with a TFT in a liquid crystaldisplay panel according to the invention (a shift register circuit);

FIG. 22 shows a diagram illustrating a circuit structure in the case offorming a scanning line driver circuit with a TFT in a liquid crystaldisplay panel according to the invention (a buffer circuit);

FIG. 23 shows a block diagram of a main structure of a liquid crystaltelevision receiver according to the invention;

FIG. 24 shows a view illustrating a structure of a liquid crystaldisplay module according to the invention;

FIG. 25 shows a view illustrating a structure of a television receiverto be completed according to the invention;

FIG. 26 shows a top view illustrating a liquid crystal display panelaccording to the invention;

FIG. 27 shows an equivalent circuit diagram of a liquid crystal displaypanel illustrated in FIG. 26; and

FIG. 28 shows a view illustrating a structure of a droplet dischargedevice applicable to the invention.

BEST MODE FOR CARRYING OUT ME INVENTION

Embodiment mode of the present invention will be explained in detailwith reference to the drawings. Note that the same reference numeralsdenote the same parts among each drawing, and the explanation will notbe repeated in the following explanations. In addition, it is to beunderstood that various changes and modifications will be apparent tothose skilled in the art, unless such changes and modifications departfrom content and the scope of the invention. Therefore, the invention isnot interpreted with limiting to the description in this embodimentmode.

FIG. 1 shows a top view of a structure of a liquid crystal display panelaccording to the present invention. A pixel portion 101 in which pixels102 are arranged in a matrix, a scanning line input terminal 103, and asignal line input terminal 104 are formed over a substrate 100 having aninsulating surface. The number of pixels may be provided according tovarious standards. The number of pixels of XGA may be 1024×768×3 (RGB),that of UXGA may be 1600×1200×3 (RGB), and that of a full-speck highvision to correspond thereto may be 1920×1080×3 (RGB).

The pixels 102 are arranged in a matrix by intersecting a scanning lineextended from the scanning line input terminal 103 with a signal lineextended from the signal line input terminal 104. Each pixel 102 isprovided with a switching element and a pixel electrode connectedthereto. A typical example of the switching element is a TFT. A gateelectrode side of a TFT is connected to the scanning line, and a sourceor drain side thereof is connected to the signal line; therefore, eachpixel can be controlled independently by a signal inputted from outside.

A TFT includes a semiconductor layer, a gate insulating layer, and agate electrode as main components. A wiring connected to one of a sourceregion and a drain region which are formed in the semiconductor layer isconcomitant thereof. A top gate type in which a semiconductor layer, agate insulating layer, and a gate electrode are sequentially arrangedfrom the substrate side, a bottom gate type in which a gate electrode, agate insulating layer, and a semiconductor layer are sequentiallyarranged from the substrate side, or the like is known as a structure ofa TFT. However, any one of structures may be applied to the invention.

An amorphous semiconductor (hereinafter also referred to as an “AS”)manufactured by a vapor phase growth method using a semiconductormaterial gas typified by silane or germane or a sputtering method; apolycrystalline semiconductor that is formed by crystallizing theamorphous semiconductor by utilizing light energy or thermal energy; asemi-amorphous (also referred to as microcrystallite ormicrocrystalline, and hereinafter also referred to as an “SAS”)semiconductor; or the like can be used for a material which forms asemiconductor layer.

An SAS is a semiconductor with an intermediate structure between anamorphous structure and a crystal structure (including a single crystaland a polycrystal). This is a semiconductor having a third conditionthat is stable in regard to a free energy, and a crystalline regionhaving a short distance order and lattice distortion is includedtherein. A crystalline region of from 0.5 nm to 20 nm can be observed atleast in a part of region in the film. When silicon is contained as themain component, Raman spectrum is shifted to a lower frequency side lessthan 520 cm⁼². Diffraction peak of (111) or (220) to be caused from acrystal lattice of silicon is observed in X-ray diffraction. At least 1atomic % or more of hydrogen or halogen is contained to terminate of adangling bond. An SAS is formed by carrying out grow dischargedecomposition (plasma CVD) on a silicide gas. In addition to SiH₄,Si₂H₆, SiH₂Cl₂, SiHCl₃, SiCl₄, SiF₄, or the like can be used for thesilicide gas. In addition, GeF₄ may be mixed. This silicide gas may bediluted with H₂ or H₂ and one or more of the rare gas element of He, Ar,Kr, and Ne. A dilution ratio ranges from 2 times to 1000 times. Apressure ranges approximately from 0.1 Pa to 133 Pa, and a powerfrequency ranges from 1 MHz to 120 MHz, preferably from 13 MHz to 60MHz. A substrate heating temperature may be 300° C. or less. It isdesirable that an atmospheric constituent impurity such as oxygen,nitrogen, or carbon is 1×10²⁰ cm⁻¹ or less as an impurity element in thefilm, specifically an oxygen concentration is 5×10¹⁹/cm³ or less,preferably 1×10¹⁹/cm³ or less.

FIG. 1 shows a structure of a liquid crystal display panel that controlsa signal inputting into a scanning line and a signal line by an externaldriver circuit. Furthermore, a driver IC may be mounted on a substrate100 by a COG (Chip on Glass) as shown in FIG. 2. FIG. 2 shows a mode inwhich a scanning line driver IC 105 and a signal line driver IC 106 aremounted on the substrate 100. The scanning line driver IC 105 isprovided between a scanning line input terminal 103 and a pixel portion101.

In addition, a TFT provided for a pixel can be formed from an SAS. Sincea TFT an SAS has an electric field effect mobility of from 1 cm²/V·secto 15 cm²/V·sec, a driver circuit can be formed. FIG. 3 shows an exampleof forming a scanning line driver circuit 107. Furthermore, a protectivecircuit 108 can be also provided between the scanning line drivercircuit 107 and a pixel portion 101. The number of input terminals canbe reduced by forming the scanning line driver circuit 107 with a overthe substrate 100.

FIG. 28 shows one mode of a droplet discharge device used for formingpatterns. Each head 1403 of a droplet discharge means 1401 isindividually connected to a control means 1404. The control means 1404controls droplet discharge from the head 1403. The timing of dischargingdroplet is controlled based on the program inputted into a computer1407. A position of discharging a droplet may be decided based on amarker 1408 formed over a substrate 100 for example. In addition, areference point may be fixed with an edge of the substrate 100 as areference. A reference point is detected by an imaging means 1402 suchas a CCD, and the computer 1407 recognizes a digital signal to which thereference point is converted by an image processing means 1406 togenerate a control signal. Of course, information of a pattern to beformed over the substrate 100 is placed in a recording medium 1405.Based on this information, the control signal can be transmitted to thecontrol means 1404 and each head 1403 of the droplet discharge means1401 can be controlled individually.

Next, a step of manufacturing a liquid crystal display panel using sucha droplet discharge device is explained hereinafter.

Embodiment Mode 1

A method for manufacturing a channel protective type thin filmtransistor and a liquid crystal display device with the use thereof areexplained in Embodiment mode 1.

FIG. 4A shows a step of forming a gate electrode and a gate wiringconnected to the gate electrode with a droplet discharge method over asubstrate 100. Note that FIG. 4A shows a longitudinal sectionalstructure, and FIG. 13 shows a planar structure corresponding to A-B andC-D thereof.

In addition to a non-alkaline glass substrate such as bariumborosilicate glass, alumino borosilicate glass, and aluminosilicateglass manufactured with a fusion method or a floating method, and aceramic substrate, a plastic substrate having the heat resistance thatcan withstand processing temperature or the like can be used for thesubstrate 100. In addition, a semiconductor substrate such as singlecrystal silicon, a substrate in which a surface of a metal substratesuch as stainless is provided with an insulating layer may be appliedtoo.

A conductive layer 201 containing a metal selected from the groupconsisting of Ti (titanium), W (tungsten), Cr (chromium), Al (aluminum),Ta (tantalum), Ni (nickel), Zr (zirconium), Hf (hafnium), V (vanadium),Ir (iridium), Nb (niobium), Pd (palladium), Pt (platinum), Mo(molybdenum), Co (cobalt), and Rh (rhodium) is preferably formed overthe substrate 100 by a method such as a sputtering method or a vapordeposition method. The conductive layer 201 may be formed to have a filmthickness of from 0.01 nm to 10 nm; however, a film structure is notnecessarily needed since it may be formed extremely thin. Note that thisconductive layer 201 is provided to form the gate electrode with goodadhesiveness. When adequate adhesiveness is obtained, the gate electrodemay be directly formed on the substrate 100 without forming theconductive layer 201.

A wiring 202, a gate electrode 203, and a capacitor wiring 204 areformed over the conductive layer 201 by discharging a compositioncontaining a conductive substance with a droplet discharge method. Thecomposition containing a metal such as silver, gold, copper, tungsten,or aluminum as the main component can be used as the conductivesubstance which forms these layers. In addition, indium tin oxide (ITO)and indium tin oxide containing silicon oxide (ITSO) which have a lighttransmitting property may be combined. Specifically, the gate wiring ispreferable to be low resistance. Therefore, a material in which any oneof gold, silver, or copper dissolved or dispersed in a solvent ispreferably used, and more preferably silver or copper with lowresistance is used in consideration of a specific resistance value.However, in the case of using silver or copper, a barrier film may beadditionally provided to protect from an impurity. A solvent correspondsto an organic solvent such as esters like butyl acetate, alcohols likeisopropyl alcohol, or acetone. Surface tension and viscosity areappropriately adjusted by adjusting concentration of solution and addinga surface activator or the like.

Since the gate electrode needs to be formed minutely, a nano pastecontaining particles of which average particle size is from 5 nm to 10nm is preferably used. In addition, the gate electrode may be formed bydischarging a composition containing particles covered the circumferenceof a conductive material with other conductive materials. For example,as for particles covered the circumference of copper with silver, aconductive particle provided with a buffer layer made from Ni or NiB(nickel boron) between copper and silver may be used. A solventcorresponds to an organic solvent such as esters like butyl acetate,alcohols like isopropyl alcohol, and acetone. Surface tension andviscosity are appropriately adjusted by adjusting concentration ofsolution and adding a surface activator or the like.

A diameter of a nozzle used in a droplet discharge method is set to befrom 0.02 μm to 100 μm (preferably, 30 μm or less), and a dischargingamount of a composition discharged from the nozzle is preferably set tobe from 0.001 pl to 100 pl (preferably, 10 pl or less). There are twotypes of an on-demand type and a continuous type for a droplet dischargemethod, both of which may be used. Furthermore, there is a piezoelectricsystem using properties that a piezoelectric material is deformable byapplying voltage and a heating system that boils a composition by aheater provided in a nozzle and discharges the composition for a nozzleto be used in a droplet discharge method, both of which may be used. Adistance between a subject and a discharge opening of a nozzle ispreferable to be made as close as possible to drop a droplet at adesired place, which is preferably set to be, from 0.1 mm to 3 mm(preferably, 1 mm or less). While keeping the relative distance, one ofthe nozzle and the subject moves and a desired pattern is drawn. Inaddition, plasma treatment may be carried out on a surface of thesubject before discharging a composition. This is to take advantage of asurface of the subject becoming hydrophilic and lyophobic when plasmatreatment is carried out. For example, it becomes hydrophilic todeionized water and it becomes lyophobic to a paste dissolved withalcohol.

A step of discharging a composition may be carried out under lowpressure so that a solvent of the composition can be volatilized whilethe composition is discharged and hit on a subject and later steps ofdrying and baking can be skipped or shortened. In a baking step of acomposition containing a conductive material, resistivity of aconductive film constructing the gate electrode can be decreased and theconductive film can be made thin and smoothed by actively using a gasmixed with oxygen of which division ratio is from 10% to 30%.

After discharging a composition, either or both steps of drying andbaking is carried out by irradiation of laser light, rapid thermalannealing, heating furnace, or the like under the atmospheric pressureor the reduced pressure. Both the steps of drying and baking are stepsof heat treatment. For example, drying is carried out at 100° C. for 3minutes and baking is carried out at temperatures from 200° C. to 350°C. for from 15 minutes to 120 minutes. In order to carry out the stepsof drying and baking well, a substrate may be heated, of whichtemperatures are set to be from 100° C. to 800° C. (preferably,temperatures from 200° C. to 350° C.), though depending on a material ofa substrate or the like. Through this step, a solvent in a compositionis volatilized or dispersant is removed chemically, and a peripheralresin cures and shrinks, thereby accelerating fusion and welding. It iscarried out under the oxygen atmosphere, the nitrogen atmosphere, or theatmospheric air. However, this step is preferable to be carried outunder an oxygen atmosphere in which a solvent decomposing or dispersinga metal element is easily removed.

A continuous-wave or a pulsed gas laser or a solid state laser may beused for irradiation of laser light. There is an excimer laser, an Arlaser, or the like as the gas laser, and there is a laser using acrystal such as YAG or YVO₄ doped with Cr, Nd, or the like as the solidstate laser. In the case of rapid thermal annealing, temperature israpidly raised by using a halogen lamp or the like under the atmosphereof inert gas to carry out heat treatment that can be finished within ashort time of from some microseconds to some minutes. By carrying outheat treatment in a short time, only the most upper-surface of a thinfilm can be substantially heated; therefore, there is advantageous thatthe base side is not affected.

A nano paste used for forming the conductive layer 201 is a matterdispersed or dissolved a conductive particle of which particle size isfrom 5 nm to 10 nm in an organic solvent, and also contains a dispersantor a thermosetting resin referred to as a binder. The binder has afunction of preventing generation of crack or uneven baked state duringbaking. According to the drying and baking steps, evaporation of theorganic solvent, degradation and removal of the dispersant, andhardening and shrinkage of the binder are carried out simultaneously;therefore, nanoparticles makes fusion and/or welding with each other tobe hardened. In this case, the nanoparticles is grown from several tensnm to several hundreds nm. The grown particles close to each other makesfusion and/or welding to connect in chain with each other to form achained metal body. On the other hand, almost all remaining organiccomponent (approximately from 80% to 90%) is pushed to outside of themetal chain body. As a result, a conductive film containing the chainedmetal body and a film made from an organic component covering theoutside of the conductive film are formed. Then, when a nano paste isbaked under the atmosphere containing nitrogen and oxygen, oxygencontained in a gas is reacted with carbon, hydrogen, or the likecontained in the film made from an organic component; therefore, thefilm made from an organic component can be removed.

In addition, when oxygen is not contained in the baking atmosphere, thefilm made from an organic component can be removed by additionallycarrying out oxygen plasma treatment or the like. In this manner, thefilm made from an organic component is removed by baking a nano pasteunder the atmosphere containing nitrogen and oxygen or by carrying outoxygen plasma treatment after drying. Therefore, the conductive filmcontaining the remaining metal chain body can be made smoothed, thin, orreduced in resistance. A solvent in a composition containing aconductive material volatilizes by discharging the composition under thelow pressure; therefore, the time for subsequent heat treatment (dryingor baking) can be shortened.

After forming the wiring 202, the gate electrode 203, and the capacitorwiring 204, it is desirable to carry out one of the following two stepsas treatment of the conductive layer 201 of which surface is exposed.

A first method is a step of forming an insulating layer 205 byinsulating the conductive layer 201 not overlapping with the wiring 202,the gate electrode 203, and the capacitor wiring 204 (see FIG. 4B). Inother words, the conductive layer 201 not overlapping with the wiring202, the gate electrode 203, and the capacitor wiring 204 are oxidizedto be insulated. In the case of insulating the conductive layer 201 inthis manner, the conductive layer 201 is preferably formed to have afilm thickness of from 0.01 nm to 10 nm, so that it becomes aninsulating layer by being oxidized. Note that either an exposing methodto the oxygen atmosphere or a method for carrying out heat treatment maybe used as an oxidizing method.

A second method is a step of etching and removing the conductive layer201, using the wiring 202, the gate electrode 203, and the capacitorwiring 204 as the masks. In the case of using this step, there is norestriction on a film thickness of the conductive layer 201.

Next, a gate insulating layer 207 is formed in a single layer or alamination by using a plasma CVD method or a sputtering method (see FIG.4C). As a specifically preferable mode, a lamination body of threelayers of a first insulating layer 208 made from silicon nitride, asecond insulating layer 209 made from silicon oxide, and a thirdinsulating layer 210 made from silicon nitride corresponds to the gateinsulating layer. Note that a rare gas such as argon may be contained ina reactive gas and mixed into an insulating film to be formed in orderto form a dense insulating film with little gate leak current at a lowdeposition temperature. Forming the first insulating layer 208 incontact with the wiring 202, the gate electrode 203, and the capacitorwiring 204 by silicon nitride or silicon oxynitride can prevent fromdeterioration by oxidation.

Next, a semiconductor layer 211 is formed. The semiconductor layer 211is formed by an AS or an SAS with a vapor phase growth method using asemiconductor material gas typified by silane or germane or a sputteringmethod.

In the case of using a plasma CVD method, an AS is formed by SiH₄ whichis a semiconductor material gas or a mixed gas of SiH₄ and H₂. When SiH₄is diluted with H₂ by from 3 times to 1000 times to make a mixed gas orwhen Si₂H₆ is diluted with GeF₄ so that a gas flow rate of Si₂H₆ to GeF₄is from 20:0.9 to 40:0.9, an SAS of which Si composition ratio is 80% ormore can be obtained. Specifically, the latter case is preferable sincethe semiconductor layer 211 can have crystallinity from an interfacewith the third insulating layer 210.

An insulating layer 212 is formed over the semiconductor layer 211 by aplasma CVD method or a sputtering method. As shown in the followingsteps, this insulating layer 212 is left over the semiconductor layer211 corresponding to the gate electrode 203 and serves as a channelprotective layer. Therefore, it is preferable that the insulating layer212 is formed of a dense film to obtain an advantageous effect ofpreventing the semiconductor layer 211 from being contaminated withimpurities such as an organic substance, a metallic substance, or watervapor to ensure cleanliness of the interface. In a glow dischargedecomposition method also, a silicon nitride film which is formed bydiluting a silicide gas by from 100 times to 500 times with a noble gassuch as argon is preferable since the dense film can be formed even at adeposition temperature of 100° C. or less. Furthermore, insulating filmsmay be laminated to be formed, if necessary.

It is possible to continuously form the gate insulating layer 207 to theinsulating layer 212 without exposing to the atmosphere. In other words,each interface between laminated layers can be formed without beingcontaminated by an atmospheric constituent and an airborne contaminatedimpurity element; therefore, variations in properties of a TFT can bereduced.

Next, a mask 213 is formed by selectively discharging a composition overthe insulating layer 212 at a position that is corresponding to the gateelectrode 203 (see FIG. 4C). A resin material such as an epoxy resin, anacrylic resin, a phenolic resin, a novolac resin, a melamine resin, or aurethane resin is used for the mask 213. In addition, the mask 213 isformed with a droplet discharge method by using an organic material suchas benzocyclobutene, parylene, flare, or light-transmitting polyimide; acompound material made from polymerization such as siloxane-basedpolymer; a composition material containing water-soluble homopolymer andwater-soluble copolymer; or the like. Alternatively, a commercial resistmaterial containing a photosensitizer may be used. For example, atypical positive type resist comprising a novolac resin andnaphthoquinonediazide compound that is a photosensitizer, and a negativetype resist comprising a base resin, diphenylsilane diol, and an acidgeneration agent may be used. In using any one of materials, surfacetension and viscosity are appropriately adjusted by diluting a solutionor adding a surface activator or the like.

The insulating layer 212 is etched by using the mask 213 in FIG. 4C, andan insulating layer 214 which functions as a channel protective layer isformed (see FIG. 5A). The mask 213 is removed, and an n-typesemiconductor layer 215 is formed over the semiconductor layer 211 andthe insulating layer 214. The n-type semiconductor layer 215 may beformed by using a silane gas and a phosphine gas and can be formed by anAS or an SAS.

Thereafter, a mask 216 is formed with a droplet discharge method on then-type semiconductor layer 215. By using this mask 216, the n-typesemiconductor layer 215 and the semiconductor layer 211 are etched.Thus, a semiconductor layer 217 and an n-type semiconductor layer 218are formed (see FIG. 5B). Note that FIG. 5A shows a longitudinalsectional structure, and FIG. 14 shows a planar structure correspondingto A-B and C-D thereof.

Subsequently, after removing the mask 216, wirings 219 and 220 connectedto a source and a drain are formed with a droplet discharge method byselectively discharging a composition containing a conductive substance(see FIG. 5B). FIG. 15 shows a planar structure corresponding to A-B andC-D shown in a longitudinal sectional structure of FIG. 5B. As shown inFIG. 15, a wiring 221 extending from one end of the substrate 100 isalso formed. The wiring 221 is provided to electrically connect to thewiring 219 connected to the source and the drain. A compositioncontaining particles of a metal such as silver, gold, copper, tungsten,or aluminum as the main component can be used as a conductive substancewhich forms this wiring. In addition, light-transmitting indium tinoxide (hereinafter also referred to as “ITO”), indium tin oxidecontaining silicon oxide (hereinafter also referred to as “ITSO”),organic indium, organotin, zinc oxide, titanium nitride, and the likemay be combined.

Next, using the wirings 219 and 220 connected to at least one of thesource and the drain as masks, n-type semiconductor layers 222 and 223functioning as source and drain regions are formed by etching the n-typesemiconductor layer 218 over the insulating layer 214 (see FIG. 5C).

Subsequently, a first electrode 224 corresponding to a pixel electrodeis formed by selectively discharging a composition containing aconductive substance to be electrically connected to the wiring 220connected to at least one of the source and the drain. In the case ofmanufacturing a transmission type liquid crystal display panel, thefirst electrode 224 may be formed a predetermined pattern by acomposition containing indium tin oxide (ITO), indium tin oxidecontaining silicon oxide (ITSO), zinc oxide (ZnO), tin oxide (SnO_(X)),or the like, and baked to form a pixel electrode. In addition, in thecase of manufacturing a reflection type liquid crystal display panel, acomposition containing particles of a metal such as silver, gold,copper, tungsten, or aluminum as the main component can be used. Asanother method, a pixel electrode layer may be formed by transparentconductive film or a light reflective conductive film by a sputteringmethod, forming a mask pattern with a droplet discharge method, andcombining an etching process (see FIG. 6A). Thus, switching TFT 233 anda capacitor element 234 is completed. Note that FIG. 6A shows alongitudinal sectional structure, and FIG. 16 shows a planar structurecorresponding to A-B and C-D thereof.

Through the above-mentioned steps, a TFT substrate 200 for a liquidcrystal display panel in which a bottom gate type (also referred to as ainversely staggered type) TFT and a pixel electrode are connected overthe substrate 100 is completed.

Next, an insulating layer 225 referred to as an alignment film is formedto cover the first electrode 224 by a printing method or a spin coatingmethod. Note that the insulating layer 225 can be selectively formed asshown in the drawing by using a screen printing method or an offsetprinting method. Rubbing treatment is carried out on the surface of theinsulating layer 225 so that orientation of a liquid crystal can becontrolled. Subsequently, a sealant 226 is formed by a droplet dischargemethod in the peripheral region where a pixel is formed (see FIG. 6B).

Thereafter, an opposite substrate 229 in which an insulating layer 227functioning as an alignment film and a second electrode 228 functioningas an opposite electrode are provided is attached to the Tier substrate200 by providing a spacer therebetween, and a liquid crystal displaypanel can be manufactured by providing the space with a liquid crystallayer 230 (see FIG. 6C). The sealant 226 may be mixed with a filler, andfurther, a color filter, a shielding film (a black matrix), or the likemay be formed over the opposite substrate 229. Note that a dispensertype (a dropping type) or a dip type (a pumping type) that is a methodof injecting a liquid crystal by using a capillary phenomenon afterattaching the opposite substrate 229 can be used as a method for formingthe liquid crystal layer 230.

A closed loop is formed with the sealant 226 in a liquid crystal dripinjection method to which a dispenser type is applied, and a liquidcrystal is dropped once or several times therein. Subsequently, thesubstrates are attached in vacuum, and then cured by UV irradiation tomake a state filled with liquid crystals after carrying out ultravioletcuring.

Next, the insulating layer formed in the same layer as that of the gateinsulating layer 207 over the wiring 202 are removed by carrying outashing treatment using an oxygen gas under the atmospheric pressure orpressure near to the atmospheric pressure (see FIG. 7). This treatmentis carried out by using an oxygen gas and one or more gas of hydrogen,CF₄, NF₃, H₂O, and CHF₃. In this step, ashing treatment is carried outafter sealing by using the opposite substrate to prevent damage orbreakdown due to static electricity; however, when there are few effectsof static, ashing treatment may be carried out at any timing.

Subsequently, a wiring board 232 for connecting to an external circuitand the wiring 202 are electrically connected. Through the above steps,a liquid crystal display panel including a channel protective typeswitching TFT 233 and a capacitor element 234 is completed. Thecapacitor element 234 is formed of the capacitor wiring 204, the gateinsulating layer, and the first electrode 224.

As mentioned above, in this embodiment mode, a liquid crystal displaydevice can be manufactured by manufacturing a TFT without alight-exposure step using a photomask. A part or all of the treatmentsuch as application of a resist, light-exposure, or developmentaccording to the light-exposure step can be skipped. In addition, aliquid crystal display device can be easily manufactured by forming eachkind of patterns directly over a substrate with a droplet dischargedmethod even when a glass substrate after fifth generation, one side ofwhich exceeds 1000 mm.

Embodiment Mode 2

Embodiment mode 1 shows a structure in which a first electrode 224 and awiring 220 connected to at least one of a source or a drain areconnected directly; however, an insulating layer may be providedtherebetween as another mode.

In this case, an insulating layer 240 functioning as a protective filmis formed when the steps up to FIG. 5C is finished (see FIG. 8A). A filmto be formed of silicon nitride or silicon oxide formed by a sputteringmethod or a plasma CVD method may be applied to this protective film. Itis necessary to form an opening 241 in the insulating layer 240, and thewiring 220 connected to at least one of the source and the drain iselectrically connected to the first electrode 224 through the opening241 (see FIG. 8B). At the time of forming the opening 241, an opening242 necessary for attaching a connection terminal later may besimultaneously formed. A TFT substrate 200 is thus completed.

A method for forming the openings 241 and 242 is not specificallylimited; however, an opening can be selectively opened by, for example,plasma etching under the atmospheric pressure. After forming a mask witha droplet discharge method, wet etching treatment may be carried out. Inaddition, the insulating layer 240 having the openings 241 and 242 canbe also directly formed by selectively forming an inorganic siloxane ororganic siloxane-based film to be formed by a droplet discharge method.

An alignment film 244 is formed as shown in FIG. 8B. Then, as well as inEmbodiment Mode 1, an opposite substrate is fixed to the TFT substrate200 by using the sealant, and a liquid crystal is injected. Thus, aliquid crystal display panel shown in FIG. 9 is completed.

Embodiment Mode 3

A method for manufacturing a channel etched type thin film transistorand a liquid crystal display device with the use thereof are explainedin Embodiment Mode 3.

A wiring 202, a gate electrode 203, and a capacitor wiring 204 areformed over a substrate 100. These are formed by directly drawing acomposition containing conductive substance over the substrate 100 witha droplet discharge method. Next, a gate insulating layer 207 is formedto have a single layer structure or a laminated structure by a plasmaCVD method or a sputtering method. A specifically preferable mode is alamination body of three layers of a first insulating layer 208including silicon nitride, a second insulating layer 209 includingsilicon oxide, and a third insulating layer 210 including siliconnitride. Furthermore, a semiconductor layer 211 functioning as an activelayer is formed. The above-mentioned steps are the same as those inEmbodiment Mode 1.

An n-type semiconductor layer 301 is formed over the semiconductor layer211 (see FIG. 10A). Next, a mask 302 is formed by selectivelydischarging a composition over the n-type semiconductor layer 301.Subsequently, the semiconductor layer 211 and the n-type semiconductorlayer 301 are simultaneously etched by using the mask 302, and asemiconductor layer 303 and an n-type semiconductor layer 304 areformed. Thereafter, wirings 305 and 306 connected to at least one of asource and a drain are formed over the n-type semiconductor layer 304 bya droplet discharge method (see FIG. 10B).

Next, using the wirings 305 and 306 connected to at least one of thesource and the drain as the masks, the n-type semiconductor layer 304 isetched, and n-type semiconductor layers 307 and 308 are formed. Thesemiconductor layer 303 is slightly etched too, and a semiconductorlayer 309 partly etched in an opening is formed. Subsequently, a firstelectrode 310 is formed to electrically connect to the wiring 306connected to at least one of the source or the drain (see FIG. 10C).

Next, an insulating layer 311 functioning as an alignment film isformed. Subsequently, a sealant 312 is formed, and the substrate 100 anda substrate 315 in which an opposite electrode 314 and an alignment film313 are formed are attached by using the sealant 312. Thereafter, aliquid crystal layer 316 is formed between the substrate 100 and thesubstrate 315. Next, a region to be attached a connection terminal 317is exposed by etching under the atmospheric pressure or pressure near tothe atmospheric pressure, and the connection terminal 317 is attached.Accordingly, a liquid crystal display device can be manufactured (seeFIG. 11).

In this embodiment mode, a liquid crystal display device can bemanufactured by manufacturing a TFT without a light-exposure step usinga photomask. A part or all of the treatment such as application of aresist, light-exposure, or development according to the light-exposurestep can be skipped. In addition, a liquid crystal display device can beeasily manufactured by forming each kind of patterns directly over asubstrate with a droplet discharged method even when a glass substrateafter fifth generation, one side of which exceeds 1000 mm.

Embodiment Mode 4

A top gate type TFT manufactured by a droplet discharge method and aliquid crystal display device with the use thereof are explained inEmbodiment Mode 4 with reference to FIG. 19.

A switching TFT 291 and a capacitor portion 293 are formed over a ‘WI’substrate 200. The switching TFT 291 and the capacitor portion 293 canbe manufactured in the following step.

First, a capacitor wiring 270, wirings 271 and 272 connected to at leastone of a source and a drain, and wiring 273 are formed by a dropletdischarge method. A composition containing particles of a metal such assilver, gold, copper, tungsten, or aluminum is used for the conductivesubstance which forms these layers. Specifically, the wirings connectedto at least one of the source and the drain are preferable to be lowresistance. Therefore, a material in which any one of gold, silver, orcopper dissolved or dispersed in a solvent is preferably used, and morepreferably silver or copper with low resistance is used in considerationof a specific resistance value. Nanoparticles of which particle size isfrom 5 nm to 10 nm is preferable to be used to form this wiring. Asolvent corresponds to organic solvent such as esters like butylacetate, alcohols like isopropyl alcohol, or acetone. Surface tensionand viscosity may be appropriately adjusted by adjusting concentrationof a solution and adding a surface activator or the like.

N-type semiconductor layers 276 and 277 are formed to be in contact withthe wirings 272 and 273 connected to at least one of the source and thedrain. Then, a semiconductor layer 278 is formed by an AS or an SAS. AnAS or an SAS is formed with a vapor phase growth method or a sputteringmethod. When a plasma CVD method, a kind of the vapor phase growthmethod, is used, an AS is formed by using SiH₄ which is a semiconductormaterial gas or a mixed gas of SiH₄ and H₂. In addition, an SAS isformed by the mixed gas by diluting SiH₄ with H₂ by from 3 times to 1000times. In the SAS formed by diluting SiH₄ with H₂, a crystal is muchmore developed on a developed surface of an SAS film than on a substrateinterface. Therefore, a combination with a top gate type TFT in which agate insulating layer 207 is formed over the semiconductor layer 278 issuitable.

The semiconductor layer 278 is formed by an AS or an SAS film over theentire surface of the substrate 100, and processed into a predeterminedshape using a mask formed by a droplet discharged method. The positionof the semiconductor layer 278 is given corresponding to the wirings 272and 273 connected to at least one of the source and the drain. In otherwords, the semiconductor layer 278 is formed to overlap with the wirings272 and 273 connected to at least one of the source and the drain. Atthis time, the n-type semiconductor layers 276 and 277 are sandwichedbetween the semiconductor layer 278 and the wirings 272 and 273connected to at least one of the source and the drain, respectively.

Then, the gate insulating layer 207 is formed to have a single layerstructure or a laminated structure by using a plasma CVD method or asputtering method. As a specifically preferable mode, the gateinsulating layer has a structure of a lamination body of three layersincluding a first insulating layer 208 made from silicon nitride, asecond insulating layer 209 made from silicon oxide, and a thirdinsulating layer 210 made from silicon nitride. In addition, the gateinsulating layer 207 is also used as an insulating layer which forms astorage capacitor by covering the capacitor wiring 270.

A gate electrode 279 is formed over the gate insulating layer 207 with adroplet discharge method. A composition containing particles of a metalsuch as silver, gold, copper, tungsten, or aluminum can be used for aconductive substance which forms the gate electrode 279. After drawingthe gate electrode 279 and a pattern of the wirings connected thereto,the gate electrode 279 is completed by baking.

The gate insulating layer 207 is etched so that the wirings 271 and 273are at least partially exposed. Then, a first electrode 274 is formed byselectively discharging a composition containing a conductive substanceto be electrically connected to the wiring 273. This first electrode 274serves as a pixel electrode in a liquid crystal display device. In thecase of manufacturing a transmission type liquid crystal display device,the first electrode 274 includes a composition containing indium tinoxide (ITO), indium tin oxide containing silicon oxide (ITSO), zincoxide (ZnO), tin oxide (SnO_(X)), or the like. In addition, the firstelectrode 274 includes indium tin oxide (ITO), indium tin oxidecontaining silicon oxide (ITSO), zinc oxide (ZnO), or the like with asputtering method. More preferably, indium tin oxide containing siliconoxide which is formed with a sputtering method by using a target inwhich 2 wt. % to 10 wt. % of silicon oxide is contained in ITO may beused. Furthermore, in the case of manufacturing a reflection type liquidcrystal display device, the first electrode 274 includes a compositioncontaining particles of a metal such as silver, copper, or aluminum in apredetermined pattern.

As mentioned above, the TFT substrate 200 over which the top gate type(also referred to as a stagger type) switching TFT 291 and the capacitorportion 293 are provided can be obtained. An insulating layer 225referred to as an alignment film is formed over the first electrode 274.The insulating layer 225 can be formed in accordance with a shape of thefirst electrode 274 by using a screen printing method or an offsetprinting method. Thereafter, an opposite substrate 229 over which aninsulating layer 227 functioning as an alignment film and a secondelectrode 228 functioning as an opposite electrode are provided isattached to the Tier substrate 200 with a spacer therebetween, and aliquid crystal layer 230 is provided in the space. A filler may becontained in a sealant 226, and further, a color filter, a shieldingfilm (black matrix), or the like may be formed over the oppositesubstrate 229. Note that a dispenser type (a dropping type) or a diptype (a pumping up type) that is a method of injecting a liquid crystalby using a capillary phenomenon after attaching the opposite substrate229 can be used as a method for forming the liquid crystal layer 230.

A closed loop is formed with the sealant 226 in a liquid crystal dripinjection method to which a dispenser type is applied, and a liquidcrystal is dropped once or several times therein. Subsequently, thesubstrates are attached in vacuum, and then cured by UV irradiation tomake a state filled with liquid crystals after carrying out ultravioletcuring. A wiring board 232 for connection is provided so as to beelectrically connected the wiring 271. The wiring board 232 provides asignal or power from outside.

According to this embodiment mode, a liquid crystal display device canbe manufactured by manufacturing a TFT without a light-exposure stepusing a photomask. In this embodiment mode, a part or all of thetreatment such as application of a resist, light-exposure, ordevelopment according to the light-exposure step can be skipped. Inaddition, a liquid crystal display device can be easily manufactured byforming each kind of patterns directly over a substrate with a dropletdischarged method even when a glass substrate after fifth generation,one side of which exceeds 1000 mm.

Embodiment Mode 5

In liquid crystal display panels manufactured by Embodiment Mode 1,Embodiment Mode 2, and Embodiment Mode 3, as explained in FIG. 3, ascanning line driver circuit can be formed over a substrate 100 byforming a semiconductor layer from SAS.

FIG. 20 shows a block diagram of the scanning line driver circuitcomposed of n-channel type TFTs using the SAS in which electric fieldeffect mobility of from 1 cm²/V·sec to 15 cm²/V·sec can be obtained.

A block shown in reference numeral 500 corresponds to a pulse outputcircuit outputting a sampling pulse for one step in FIG. 20, and a shiftregister is composed of n pieces of pulse output circuit. Referencenumeral 501 denotes a buffer circuit, and a pixel 502 is connected atthe ends thereof.

FIG. 21 shows a specific structure of the pulse output circuit 500, andthe circuit is composed of n-channel type TFTs 601 to 613. At this time,the size of the TFTs may be decided in consideration of an operatingcharacteristic of the n-channel type TFTs using SAS. For example, when achannel length is set to be 8 μm, the channel width can be set rangingfrom 10 μm to 80 μm.

In addition, FIG. 22 shows a specific structure of the buffer circuit501. The buffer circuit is composed of n-channel type TFTs 620 to 635 inthe same manner. At this time, the size of the TFTs may be decided inconsideration of an operating characteristic of the n-channel type TFTsusing SAS. For example, when a channel length is set to be 10 μm, thechannel width can be set ranging from 10 μm to 1800 μm.

It is necessary to connect the TFTs with each other by wirings torealize such a circuit, and FIG. 12 shows a structure example of wiringsin the case thereof. FIG. 12 shows a state in which a gate electrode203, a gate insulating layer 207, a semiconductor layer 217 formed froman SAS, an insulating layer 214 which forms a channel protective layer,n-type semiconductor layers 222 and 223 which forms a source and adrain, and wirings 219 and 220 connected to at least one of the sourceand the drain are formed. In this case, connection wirings 235, 236, and237 and gate electrode 203 are formed over the substrate 100 in the samestep. Openings are provided in the gate insulating layer 207 so that theconnection wirings 235, 236, and 237 are exposed. Various kinds ofcircuits can be realized by connecting the TFTs appropriately by thewirings 219 and 220 connected to the source and the drain and aconnection wiring 238 formed in the same step.

Embodiment Mode 6

One mode in which a protective diode is provided for a scanning lineinput terminal portion and a signal line input terminal portion isexplained with reference to FIG. 26. A TFT 260 and a capacitor element265 are provided for a pixel 102 in FIG. 26. The TFT 260 and thecapacitor element 265 have the same structure as the switching TFT 233and the capacitor element 234 in Embodiment Mode 1, respectively.

Protective diodes 261 and 262 are provided for the signal line inputterminal portion. These protective diodes are manufactured in the samestep as that of the WI 260 and being operated as a diode by being eachconnected to a gate and one of a drain or a source. FIG. 27 shows anequivalent circuit diagram of a top view shown in FIG. 26.

The protective diode 261 includes a gate electrode 250, a semiconductorlayer 251, an insulating layer for channel protection 252, and a wiring253. The protective diode 262 has the same structure. Common potentiallines 254 and 255 connecting to this protective diode are formed in thesame layer as that of the gate electrode. Therefore, it is necessary toform a contact hole in a gate insulating layer to electrically connectto the wiring 253.

A mask may be formed by a droplet discharge method and etching processmay be carried out to form a contact hole in the gate insulating layer.In this case, when etching process by atmospheric pressure discharge isapplied, local discharge process is also possible, and it does not needto form a mask over an entire surface of a substrate.

The protective diode 261 or 262 is formed in the same layer as that of awiring 219 connected to the source and the drain in the TFT 260 and hasa structure in which a wiring 256 connected thereto is connected to asource side or a drain side.

The input terminal portion of the scanning signal line side also has thesame structure. Protective diodes 263 and 264 are provided for thescanning line input terminal portion. These protective diodes aremanufactured in the same step as that of the TFT 260 and operated as adiode by being each connected to the gate and one of the drain or thesource. According to the present invention, the protective diodesprovided in an input stage can be formed at the same time. Note that theposition of depositing a protective diode is not limited to thisembodiment mode and can be also provided between a driver circuit and apixel as shown in FIG. 3.

Embodiment Mode 7

First, a liquid crystal display device to which a COG method is appliedis explained with reference to FIGS. 17A and 17B. FIGS. 17A and 17B eachshow a liquid crystal display device in which a pixel portion 1002displaying information such as a character or an image and scanning linedriver circuits 1003 and 1004 are provided over a substrate 1001.

In FIG. 17A, individual driver circuit (hereinafter referred to as adriver IC) is taken out by separating a mother substrate 1005 over whicha plurality of driver circuits is formed. The same glass substrate usedfor a liquid crystal display device can be used for the mother substrate1005. For example, driver ICs 1007 can be obtained by forming aplurality of driver ICs on a rectangular glass substrate of which oneside is, for example, from 300 mm to 1000 mm or more and by separatingit. The driver ICs 1007 are separated by forming it in a rectangularshape of which major axis is from 15 mm to 80 mm and minor axis is from1 mm to 6 mm in consideration of a length of one side of the pixelportion or a pixel pitch. A cost of part can be reduced by forming thedriver ICs over the mother substrate 1005 with a TFT using a crystallinesemiconductor film.

FIG. 17A shows a mode in which a plurality of the driver ICs 1007 ismounted on the substrate 1001 and has a structure in which a signal isinputted from an external circuit by connecting a flexible wiring 1006at the end of the driver ICs 1007. FIG. 17B shows a structure in which along driver IC 1010 cut from a large-sized substrate 1008 is mounted onthe substrate 1001. A mode in which a flexible wiring 1009 is mounted onat the end of the long driver IC 1010 is shown. The number of parts canbe reduced and the number of steps can be reduced by using such a longdriver IC.

Next, a liquid crystal display device to which a TAB method is adoptedis explained with reference to FIGS. 18A and 18B. A pixel portion 1002and scanning line driver circuits 1003 and 1004 are provided over asubstrate 1001. In FIG. 18A, a plurality of flexible wirings 1006 isattached to the substrate 1001. Driver ICs 1007 are mounted on theflexible wirings 1006. FIG. 18B shows a mode in which a flexible wiring1009 is attached to the substrate 1001 and a driver IC 1010 is mountedon the flexible wiring 1009. In the case of applying the latter, metalpieces or the like that fixes the driver IC 1010 may be attachedtogether in respect of intensity. The number of parts can be reduced andthe number of steps can be reduced by using such a long driver IC.

The restriction specifically on a length of a major axis is relieved byforming the driver IC over the glass substrate as in FIGS. 17A and 17Band FIGS. 18A and 18B, and less number necessary for mountingcorresponding to the pixel region 1002 is needed. In other words, a longdriver IC formed to include single crystal silicon cannot be realizeddue to mechanical strength or restriction of a substrate. When a driverIC is formed over a glass substrate, the driver IC does not loseproductivity since it is not limited to a shape of a substrate used as amother body. This is a large predominant respect as compared with thecase of taking out IC chips from a circular silicon wafer.

The driver ICs 1007 and 1010 shown in FIGS. 17A and 1713 and FIGS. 18Aand 18B are signal line driver circuits. In order to form a pixel regioncorresponding to a RGB full color, 3072 signal lines in a XGA class and4800 signal lines in a UXGA class are necessary. The signal lines ofsuch a number forms a leading out line by dividing into several blocksat an edge of the pixel region 1002 and is gathered in accordance with apitch of an output terminal of the driver IC 1007.

The driver IC is preferably formed to include a crystallinesemiconductor over a substrate. The crystalline semiconductor formed bybeing irradiated with a continuous-wave laser is superior. Therefore, acontinuous-wave solid state laser or a gas laser is used as anoscillator in which the laser light is generated. A transistor can beformed using a polycrystalline semiconductor layer with a large grainsize having less crystal defect. In addition, high-speed driving ispossible since mobility or a response speed is favorable, and it ispossible to further improve an operating frequency of an element thanthat of the conventional element. Further, high reliability can beobtained since there are few properties variations. Note that achannel-length direction of a transistor and a scanning direction oflaser light may be accorded with each other to further improve anoperating frequency. This is because the highest mobility can beobtained when a channel length direction of a transistor and a scanningdirection of laser light with respect to a substrate are almost parallel(preferably, from −30° to 30°) in a step of laser crystallization by acontinuous-wave laser. A channel length direction coincides with adirection of current floating in a channel formation region, in otherwords, a direction in which an electric charge moves. The transistorthus manufactured has an active layer composed of a polycrystallinesemiconductor layer in which a crystal grain is extended in a channeldirection, and this means that a crystal grain boundary is formed almostalong a channel direction.

In carrying out laser crystallization, it is preferable to narrow downthe laser light considerably, and a beam spot thereof preferably has awidth of approximately from 1 mm to 3 mm as same as that of a minor axisof the driver ICs. In addition, in order to ensure an enough andeffective energy density to an object to be irradiated, an irradiatedregion of the laser light is preferably a linear shape. However, alinear shape here does not refer to a line in a proper sense, but refersto a rectangle or an oblong with a large aspect ratio. For example, thelinear shape refers to a rectangle or an oblong with an aspect ratio of2 or more (preferably from 10 to 10000). Accordingly, productivity canbe improved by conforming a width of a beam spot of the laser light tothat of a minor axis of the driver ICs.

In FIGS. 17A and 17B and FIGS. 18A and 18B, the scanning line drivercircuit is integrally formed with the pixel portion and the driver IC ismounted as a signal line driver circuit. However, this embodiment modeis not limited thereto, and the driver IC may be mounted as both ascanning line driver circuit and a signal line driver circuit. In thatcase, it is preferable to differentiate a specification of the driverICs to be used between the scanning line side and signal line side. Forexample, a withstand pressure of around 30 V is required for thetransistor composing the scanning line driver ICs; however, a drivefrequency is 100 kHz or less and a high speed operation is comparativelynot required. Therefore, it is preferable to set a sufficiently longchannel-length (L) of the transistor composing the scanning line driver.On the other hand, a withstand pressure of around 12 V is enough for thetransistor of the signal line driver ICs; however, a drive frequency isaround 65 MHz at 3 V and a high speed operation is required. Therefore,it is preferable to set a channel-length or the like of the transistorcomposing a driver with a micron rule.

In the pixel region 1002, the signal line and the scanning line areintersected to form a matrix and a transistor is arranged in accordancewith each intersection. A TFT having a structure in which a channel isformed to include amorphous semiconductor or a semi-amorphoussemiconductor can be used as the transistor arranged in the pixelportion 1002 in this embodiment mode. An amorphous semiconductor isformed by a method such as a plasma CVD method or a sputtering method.It is possible to form a semi-amorphous semiconductor at a temperatureof 300° C. or less with plasma CVD. Therefore, a film thicknessnecessary to form a transistor is formed in a short time even in thecase of a non-alkaline glass substrate of an external size of, forexample, 550 mm×650 mm. The feature of such a manufacturing technique iseffective in manufacturing a liquid crystal display device of alarge-sized screen. In addition, a semi-amorphous TFT can obtainelectron field-effect mobility of 1 cm²/V·sec to 15 cm²/V·sec by forminga channel formation region to include SAS. Therefore, this TFT can beused as a switching element of pixels and as an element which composesthe scanning line driver circuit.

As mentioned above, the driver circuit can be incorporated into a liquidcrystal display panel. According to this embodiment mode, a liquidcrystal display device can be easily manufactured even by using a glasssubstrate after fifth generation, one side of which exceeds 1000 mm.

Embodiment Mode 8

A liquid crystal display television receiver can be completed by aliquid crystal display panel manufactured by Embodiment Mode 7. FIG. 23shows a block diagram of a main structure of the liquid crystal displayreceiver. A liquid crystal display panel can be formed in any manners asfollows: in case where only the pixel portion 401 is formed, and thenthe scanning line driver circuit 403 and the signal line driver circuit402 are mounted by a TAB method as shown in FIG. 1; the pixel portion401 and the scanning line driver circuit 403 and the signal line drivercircuit 402 which are peripheral thereof are formed by COG method asshown FIG. 2; and in the case where a TFT is formed to include SAS, thepixel portion 401 and the scanning line driver circuit 403 is integrallyformed over the substrate, and the signal line driver circuit 402 isseparately mounted as a driver IC.

Another structure of an external circuit comprises a video waveamplifier circuit 405 which amplifies a video signal received by a tuner404; a video signal processing circuit 406 which converts the videosignal outputted therefrom into a color signal corresponding to eachcolor of red, green, and blue; a control circuit 407 which converts thevideo signal into an input specification of a driver IC; and the like.The control circuit 407 outputs the signal into the scanning line sideand the signal line side, respectively. In the case of digital driving,a signal division circuit 408 is provided on the signal line side so asto have a structure in which an input digital signal is provided bydividing into m-pieces.

Among a signal received from the tuner 404, an audio signal istransmitted to an audio wave amplifier circuit 409, and the outputthereof is provided for a speaker 413 through an audio signal processingcircuit 410. A control circuit 411 receives control information of areceiving station (a receiving frequency) or sound volume from an inputportion 412 and transmits the signal to the tuner 404 or the audiosignal processing circuit 410.

FIG. 24 is an example of a liquid crystal display module. A TFTsubstrate 200 and an opposite substrate 229 are fixed by a sealant 226,and a pixel portion 101 and a liquid crystal layer 230 are providedtherebetween to form a display region. A colored layer 268 is needed incarrying out color display. In the case of RGB system, the colored layer268 corresponding to each color of red, green, and blue is providedcorresponding to each pixel. Polarizing plates 266 and 267 are providedoutside of the substrate 200 and the opposite substrate 229. Lightsource is composed of a cold cathode tube 258 and a light conductingplate 259, and a circuit board 257 is connected to the TFT substrate 200by a wiring board 232 and an external circuit such as a control circuitor a power supply circuit are incorporated.

FIG. 25 shows the television receiver completed by incorporating thisliquid crystal display module into a casing 801. A display screen 802 isformed by the liquid crystal display module and provided a speaker 803,operation switches 804, and the like as other attached equipment.Accordingly, the television receiver can be completed according to thepresent invention.

Of course, the invention is not limited to the television receiver andis applicable to a display medium with a large-sized area such as aninformation display board at a station, an airport, or the like, or anadvertisement display board on the street as well as a monitor of apersonal computer.

This application is based on Japanese Patent Application serial no.2003-368166 filed in Japan Patent Office on 28 Oct. 2003, the contentsof which are hereby incorporated by reference.

Although the invention has been fully described by way of EmbodimentModes and with reference to the accompanying drawings, it is to beunderstood that various changes and modifications will be apparent tothose skilled in the art. Therefore, unless such changes andmodifications depart from the scope of the invention hereinafterdefined, they should be constructed as being included therein.

What is claimed is:
 1. A display device comprising: a thin filmtransistor over a substrate; and a pixel electrode connected to the thinfilm transistor, wherein the thin film transistor comprises: a gateelectrode comprising a chained metal body of particles over thesubstrate, a first layer including at least one of silicon nitride andsilicon nitride oxide over and in direct contact with the gateelectrode, a second layer including silicon oxide over and in directcontact with the first layer, and a semiconductor layer including achannel formation region over the second layer, wherein the channelformation region is provided so as to overlap the gate electrode.
 2. Thedisplay device according to claim 1, wherein the particles in thechained metal body are nanoparticles.
 3. The display device according toclaim 1, wherein the chained metal body of particles comprises Ag. 4.The display device according to claim 1, wherein the semiconductor layercomprises at least one of hydrogen and halogen; and wherein thesemiconductor layer is a semi-amorphous semiconductor having a crystalstructure.
 5. The display device according to claim 1, wherein thesemiconductor layer includes hydrogen and halogen, wherein thesemiconductor layer has a crystal structure, and wherein the thin filmtransistor is capable of being operated in electric field effectmobility of from 1 cm²/V×sec to 15 cm²/V×sec.
 6. A display devicecomprising: a thin film transistor over a substrate; and a pixelelectrode connected to the thin film transistor, wherein the thin filmtransistor comprises: a gate electrode comprising a chained metal bodyof particles over the substrate, a first layer including at least one ofsilicon nitride and silicon nitride oxide over and in direct contactwith the gate electrode, a second layer including silicon oxide over thefirst layer, a semiconductor layer including a channel formation regionover the second layer, wherein the channel formation region is providedso as to overlap the gate electrode; a first wiring and a second wiringover the semiconductor layer; and a third layer including at least oneof silicon nitride and silicon oxide formed on and in direct contactwith the first wiring and the second wiring, wherein the first wiringand the second wiring comprise a chained metal body of particles, andwherein the first wiring is connected to a first region in thesemiconductor layer and the second wiring is connected to a secondregion in the semiconductor layer.
 7. The display device according toclaim 6, wherein the particles in the chained metal body arenanoparticles.
 8. The display device according to claim 6, wherein thechained metal body of particles comprises Ag.
 9. The display deviceaccording to claim 6, wherein the semiconductor layer comprises at leastone of hydrogen and halogen; and wherein the semiconductor layer is asemi-amorphous semiconductor having a crystal structure.
 10. The displaydevice according to claim 6, wherein the semiconductor layer includeshydrogen and halogen, wherein the semiconductor layer has a crystalstructure, and wherein the thin film transistor is capable of beingoperated in electric field effect mobility of from 1 cm²/V×sec to 15cm²/V×sec.
 11. A display device comprising: a first thin film transistorover a substrate; a pixel electrode connected to the first thin filmtransistor; a driver circuit comprising a second thin film transistorwhich comprises the same layer structure as the first thin filmtransistor; and a wiring extending from the driver circuit and connectedto a gate electrode of the first thin film transistor, wherein the firstthin film transistor comprises: the gate electrode comprising a chainedmetal body of particles over the substrate, a first layer including atleast one of silicon nitride and silicon nitride oxide over and indirect contact with the gate electrode, a second layer including siliconoxide over and in direct contact with the first layer, and asemiconductor layer including a channel formation region over the secondlayer, wherein the channel formation region is provided so as to overlapthe gate electrode.
 12. The display device according to claim 11,wherein the particles in the chained metal body are nanoparticles. 13.The display device according to claim 11, wherein the chained metal bodyof particles comprises Ag.
 14. The display device according to claim 11,wherein the semiconductor layer comprises at least one of hydrogen andhalogen; and wherein the semiconductor layer is a semi-amorphoussemiconductor having a crystal structure.
 15. The display deviceaccording to claim 11, wherein all of thin film transistors contained inthe driver circuit are n-channel type thin film transistors.
 16. Thedisplay device according to claim 11, wherein each of the semiconductorlayer of the first thin film transistor and a semiconductor layer of thesecond thin film transistor includes hydrogen and halogen, wherein eachof the semiconductor layer of the first thin film transistor and thesemiconductor layer of the second thin film transistor has a crystalstructure, and wherein the first thin film transistor and the secondthin film transistor are capable of being operated in electric fieldeffect mobility of from 1 cm²/V×sec to 15 cm²/V×sec.
 17. A displaydevice comprising: a first thin film transistor over a substrate; apixel electrode connected to the first thin film transistor; a drivercircuit comprising a second thin film transistor which comprises thesame layer structure as the first thin film transistor; and a firstwiring extending from the driver circuit and connected to a gateelectrode of the first thin film transistor, wherein the first thin filmtransistor comprises: the gate electrode comprising a chained metal bodyof particles over the substrate, a first layer including at least one ofsilicon nitride and silicon nitride oxide over and in direct contactwith the gate electrode, a second layer including silicon oxide over thefirst layer, a semiconductor layer including a channel formation regionover the second layer, wherein the channel formation region is providedso as to overlap the gate electrode; a second wiring and a third wiringover the semiconductor layer; and a third layer including at least oneof silicon nitride and silicon oxide formed on and in direct contactwith the second wiring and the third wiring, wherein the second wiringand the third wiring comprise a chained metal body of particles, andwherein the second wiring is connected to a first region in thesemiconductor layer and the third wiring is connected to a second regionin the semiconductor layer.
 18. The display device according to claim17, wherein the particles in the chained metal body are nanoparticles.19. The display device according to claim 17, wherein the chained metalbody of particles comprises Ag.
 20. The display device according toclaim 17, wherein the semiconductor layer comprises at least one ofhydrogen and halogen; and wherein the semiconductor layer is asemi-amorphous semiconductor having a crystal structure.
 21. The displaydevice according to claim 17, wherein all of thin film transistorscontained in the driver circuit are n-channel type thin filmtransistors.
 22. The display device according to claim 17, wherein eachof the semiconductor layer of the first thin film transistor and asemiconductor layer of the second thin film transistor includes hydrogenand halogen, wherein each of the semiconductor layer of the first thinfilm transistor and the semiconductor layer of the second thin filmtransistor has a crystal structure, and wherein the first thin filmtransistor and the second thin film transistor are capable of beingoperated in electric field effect mobility of from 1 cm²/V×sec to 15cm²/V×sec.
 23. The display device according to claim 1, wherein a cornerportion of the gate electrode is rounded in cross-section.
 24. Thedisplay device according to claim 6, wherein a corner portion of thegate electrode is rounded in cross-section, and wherein a corner portionof the first wiring and a corner portion of the second wiring arerounded in cross-section.
 25. The display device according to claim 11,wherein a corner portion of the gate electrode is rounded incross-section.
 26. The display device according to claim 17, wherein acorner portion of the gate electrode is rounded in cross-section, andwherein a corner portion of the second wiring and a corner portion ofthe third wiring are rounded in cross-section.